OP0100 DNA METHYLATION PATTERNS IN CD4+ T CELLS DISCERN SKIN PSORIASIS FROM PSORIATIC ARTHRITIS
Authors: V. Natoli, A. Charras, S. Hofmann, S. Northey, S. Russ, F. Schulze, S. Abraham, C. Hedrich
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Psoriasis is a systemic inflammatory disease that primarily affects the skin. Approximately one third of psoriasis patients develop joint involvement and are therefore diagnosed with psoriatic arthritis (PsA). While, in adults, the development of arthritis usually follows skin psoriasis, approximately 15% of patients experience arthritis simultaneously or prior to skin disease. Thus, PsA can be missed, leading to disease progression, damage, and reduced quality of life. Individualized care is complicated by the absence of disease- or outcome-specific biomarkers. While the pathophysiology of psoriasis is incompletely understood, a key role of effector T-cells has been established. Recent studies linked altered DNA methylation with T-cell dysregulation and phenotypical variation between patients. <h3>Objectives</h3> This project aimed to identify disease-associated DNA methylation signatures in CD4<sup>+</sup> T-cells from psoriasis and PsA patients as compared to healthy controls that may be used as diagnostic and/or prognostic biomarkers and inform future treatment. <h3>Methods</h3> Peripheral blood samples were collected from 9 healthy controls, 11 skin psoriasis and 8 PsA patients. PBMCs were isolated <i>ex vivo</i>, CD4<sup>+</sup> T-cells were FACS separated, and genomic DNA was isolated. DNA methylation profiling was performed using the Illumina Human Methylation EPIC 850K platform. Bioinformatic analyses, including gene ontology (GO) and KEGG pathway analysis, were performed using R software (<i>minfi</i>, <i>limma</i>, <i>ChAMP</i>, <i>DMRcate</i>, <i>clusterProfiler</i>). Flow cytometry datasets were analyzed using <i>FlowJo</i>. To identify genes under the control of interferon (IFN), the <i>Interferome</i> database was consulted. DNA Methylation Scores were calculated for type I and type II interferons following the method suggested by Björk <i>et al.</i> (2020). <h3>Results</h3> Numbers and proportions of CD4<sup>+</sup> T-cells did not vary between controls and patients with skin psoriasis or PsA. Furthermore, no differences between controls and patient groups were observed in the proportion of CD4<sup>+</sup> T-cell subsets (naïve, central memory, effector memory, CD45RA re-expressing effector memory cells). We detected 820 differentially methylated positions (DMPs) affecting 433 genes in CD4<sup>+</sup> T-cells from healthy controls when compared to psoriasis and PsA patients. Based on DMP analyses, groups segregated in principal component (PCA) or partial least-squares discriminant analyses (PLS-DA) (Figure 1). Separation in PLS-DA was centrally influenced by two CGs (cg07021052, cg10687131) localized in <i>GDF7</i> (Growth and Differentiation factor 7), which affects T-cell regulatory factors FOXP3 and CTLA4. GO analysis of genes with at least one DMP in their promoter region delivered hypomethylation of genes involved in "negative regulation of focal adhesion assembly", "cell-substrate junction organization" and "regulation of the triglyceride biosynthetic". DNA methylation profiles (855 DMPs affecting 551 genes) distinguished between skin psoriasis and PsA patients; a high proportion of DMPs associated with interferon-regulated genes (68% total: 8.8% type I, 33.5% type II, 23.8% type I and II IFN). GO analysis delivered an enrichment of hypomethylated genes affecting "carboxylic ester hydrolase", "alkyl or aryl group transferase" and "glutathione transferase activity". Notably, we observed a majority DMPs in IFN-related genes when comparing healthy controls with PsA patients (61.9% total: 9.1% type I, 29% type II, 23.8% type I and II IFN) and controls with skin psoriasis patients (62.7% total, 7.7% type I, 31% type II, 24% type I and II IFN). Moreover, DNA methylation calculated for type I and type II IFN-associated genes significantly differed between healthy controls, skin psoriasis and PsA patients. <h3>Conclusion</h3> DNA methylation profiles in CD4+ T-cells discriminate between controls, skin psoriasis and PsA. As DNA methylation signatures may predict disease progression from psoriasis to PsA, they may be applied for molecular patient stratification towards future individualized treatment and care. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.